From the book

Another important way to make pages easy to grasp in a hurry is to make sure that the appearance of the things on the page—all of the visual cues—accurately portray the relationships between the things on the page: which things are most important, which things are similar, and which things are part of other things. In other words, each page should have a clear visual hierarchy.

Pages with a clear visual hierarchy have three traits:

The more important something is, the more prominent it is. The most important elements are either larger, bolder, in a distinctive color, set off by more white space, or nearer the top of the page—or some combination of the above.

Things that are related logically are related visually. For instance, you can show that things are similar by grouping them together under a heading, displaying them in the same visual style, or putting them all in a clearly defined area.

Things are “nested” visually to show what’s part of what. For instance, a site section name (“Computer Books”) would appear above the titles of the individual books, reflecting the fact that the books are part of the section. And each book title in turn would span all the elements that make up the description of that book.

There’s nothing new about visual hierarchies. Every newspaper page, for instance, uses prominence, grouping, and nesting to give us useful information about the contents of the page before we read a word. This picture goes with this story because they’re both spanned by this headline. This story is the most important because it has the biggest headline and a prominent position on the page.

We all parse visual hierarchies every day, but it happens so quickly that the only time we’re even vaguely aware that we’re doing it is when we can’t do it—when the visual cues (or absence of them) force us to think.

A good visual hierarchy saves us work by preprocessing the page for us, organizing and prioritizing its contents in a way that we can grasp almost instantly.

But when a page doesn’t have a clear visual hierarchy—if everything looks equally important, for instance—we’re reduced to the much slower process of scanning the page for revealing words and phrases and then trying to form our own sense of what’s important and how things are organized. It’s a lot more work.

Parsing a page with a visual hierarchy that’s even slightly flawed—where a heading spans things that aren’t part of it, for instance—is like reading a carelessly constructed sentence (“Bill put the cat on the table for a minute because it was a little wobbly”).

This flawed visual hierarchy suggests that all the major sections of the site are part of the Computer Books subsection.

Putting the heading where it belongs makes the relationship clearer.

Even though we can usually figure out what the sentence is supposed to mean, it still throws us momentarily and forces us to think when we shouldn’t have to.